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QRS

Abbreviation for quasi-random signal. A signal consisting of a bit sequence that approximates a random signal. [T1.201-1989] The unframed QRS (QRSS, QRTS, QRW) for DS1 consists of a PRBS with a 20-stage shift register with a constraint that forces the “put to a one” when the next 14 bits in the sequence would be zeros. The QRS generates every combination of 20-bit words, repeats every 1,048,575 bits, and contains high density sequences, low density sequences, and sequences that change from low density to high density and vice versa. When transmitted as the payload of a DS1 signal (framed), the QRS meets the pulse density definition “a” criteria, providing a maximum of 15-sequential zeros (14 + 1 when the frame bit is a zero), but does not meet the pulse density definition “b” criteria. (ANSI Tl.403 states: ‘the quasi-random signal may be transmitted without meeting these pulse density constraints.’) [T1.Rpt25-1993] Contrast with pseudorandom number sequence.


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